When machining a work piece, the piece must be securely mounted in a vise on the machine so that the forces of machining do not move the piece and destroy precision. The mounting of the piece in the vise may consume a considerable portion of the labor cost of machining. It is often desirable to machine one or both jaws, so that a work piece may be more effectively held therein against the machining forces. Vise jaws are complex and expensive to replace once they have been altered for a particular task. U.S. Pat. No. 5,893,551 issued Apr. 13, 1999 to Cousins et al. and U.S. Pat. No. 5,649,694 issued Jul. 22, 1997 to Buck teach machine vises with dovetail connected jaws. It would be useful to provide a jaw assembly for vises that would allow use of an inexpensive, easily machined, plate for the jaw that could be replaced with minimal effort and cost.